1. Field of the Invention
This invention concerns adhesive formulations and related methods of adhesion involving the use of materials sensitive to radiation. More particularly, this invention relates to adhesives which are adapted to being cured or set on demand by application of radiant energy, especially visible or ultraviolet light. Such adhesives are formulated employing a major proportion of certain silane species. Optionally, these formulations may contain non-silaneous polymerizable ethylenically unsaturated materials such as acrylic species. According to a preferred embodiment, such adhesives may be used for various adhesive applications in dentistry.
It has been desired to employ as adhesives formulations which are suitable for use in "demand settable" adhesive processes. Such a process would employ adhesives which do not begin to cure or harden until a preselected point in time and then are set in a relatively short period of time after curing is initiated.
It has also been desired to employ certain silane species in adhesive formulations. Such employment of silanes has been thought to lend certain beneficial properties to the adhesives thus constituted. Accordingly, such adhesives are believed to be relatively impervious to water and to coat surfaces to be joined in a desirably uniform manner. For certain adhesive uses, it is desirable to employ adhesives which are not easily degraded by heat. In typical commercial adhesives, the application of high temperatures tends to cause thermal breakdown of the compositions with concomitant loss of physical and chemical properties and liberation of noxious odors. At present, only a limited number of adhesives, such as the zinc and other metal phosphates, and certain epoxy and phenolic resins are well adapted for resistance to thermal degradation; none of these is demand settable.
2. Description of the Prior Art
It has been known to employ certain silanes in polymerizable compositions including radiation polymerizable compositions. Such employment has usually been for the purpose of securing good bonding of resin matrices with fillers or with substrates. Silanes have also been employed for viscosity modification of resin systems. The usual mode of polymerization of silanes in polymerizable resins is thermal; radical inhibitors are frequently included to prevent premature thermal polymerization. It has not been known to employ silanes as principal constituents of actinic light polymerization compositions; it has generally been thought that photopolymerization of such resins would proceed sluggishly. Use of silanes as polymerizable constituents of demand set adhesives has been, accordingly, unknown.